1. Field of the Invention
The present invention relates to an antiskid apparatus for a hybrid vehicle which is driven by a plurality of driving sources such as an engine and a motor, and a vehicle and a motorcycle provided with the antiskid apparatus.
2. Description of the Related Art
For engine-driven type vehicles, emitted environmental pollutants are desirably reduced as much as possible from an environmental point of view. Accordingly, in recent years, hybrid vehicles in which an electric motor that drives a wheel is mounted together with an engine so that the driving wheel is driven by the electric motor have been developed and are replacing engine-driven type vehicles.
As such hybrid vehicles, series-hybrid type vehicles are known in which a generator is driven by the engine and a driving motor that drives the driving wheel is driven by the electric power generated by the generator. Moreover, parallel-hybrid type vehicles are known in which the engine and the motor are switched between each other depending on the driving state and/or the remaining amount of electricity in a battery (secondary cell) charged by the generator, and at least one of the engine and the motor is used to drive the driving wheel.
In such a parallel-hybrid type vehicle, if an accelerator pedal is suddenly returned to a fully closed state while the engine is operating at a high rotation speed, the rear wheel, a driving wheel, may exceed its grip limit and slip due to a negative torque (reverse torque or so-called engine brake) of the engine.
Similarly, when the engine rotation increases due to shift down during strong deceleration associated with a braking operation, a deceleration ratio of the transmission becomes large once a clutch is engaged, and a negative torque of the engine is increased and added to a previous braking force. As a result, the rear wheel, which is the driving wheel, may exceed the grip limit and slip.
As a mechanism for reducing the occurrence of slip of the driving wheel, a drive controller such as that disclosed in Japanese Patent No. 3646632 is known and monitors the driving state of a vehicle equipped with a continuously variable transmission (CVT) to determine whether the vehicle is slipping, i.e., in a skid state.
The drive controller avoids, if the vehicle is in a skid state, the skid state by controlling the torque transmitted from the driving wheel by controlling the generator.
The drive controller described in Japanese Patent No. 3646632 is mounted on a CVT and reduces skidding of the vehicle once it has occurred. Specifically, the drive controller is configured to reduce skidding afterward on the basis of the occurrence of skidding. Recently, there has been a demand for an apparatus which can avoid skidding more effectively than drive controllers configured to reduce skidding after it has occurred.
As described above, the apparatus for reducing skidding is mounted on a CVT, and there has been also a demand for smooth driving without causing skidding in the parallel-hybrid type vehicle including a stepped transmission.
Moreover, regarding a parallel-hybrid type motorcycle as the parallel-hybrid vehicle including a stepped transmission, there has been also a demand for smooth driving without skidding.
As a mechanism for reducing the slip of the driving wheel in motorcycles, a slipper clutch that automatically limits a torque transmitted from the driving wheel, i.e., a back torque limiter (also referred to as a BTL) is widely known. In general, the BTL is disposed on the engine side from a shift gear in a power transmission path so as to perform an operation of limiting a reverse torque acting on the BTL itself. As a result, since the reverse torque limited by the BTL or the reverse torque in the rear wheel shaft is transmitted to the rear wheel shaft through a gear stage, the reverse torque varies depending on the gear stage used during the operation.
Specifically, the reverse torque limited in the rear wheel shaft is determined depending on a set gear ratio. For example, the reverse torque limited in the rear wheel shaft is different between a high-speed gear stage (e.g., shift down from a sixth speed to a fifth speed) and an intermediate-speed gear stage (e.g., shift down from a fourth speed to a third speed) or a low-speed gear stage (e.g., shift down from a second speed to a first speed) at which the BTL is operated.
As a result, a reverse torque limit set corresponding to a specific gear shift stage may not provide a setting for suitable operation for other gear stages. Specifically, if a reverse torque limit is set for operation suitable for the low-speed gear stage, the BTL can easily be operated at the high-speed gear stage, which causes a problem of lack of the engine brake. Therefore, even in the case of the motorcycle on which the BTL is mounted, achievement of smooth driving without slip is in demand.